It is known that various homogeneous catalysts or heterogeneous catalysts which possess either acidic or basic sites catalyze the so-called aldol condensation of ketones to give higher molecular weight ketones. In this condensation, the carbon atom bearing the oxo group in a first ketone molecule acts as an electrophile and attacks the carbon atom alpha to the oxo-bearing carbon atom in a second ketone molecule, with removal of a hydrogen atom from the alpha carbon atom of the second compound and protonation of the oxo oxygen atom in the first compound. The reaction may be run in the presence of hydrogen and of a hydrogenation catalyst to give a saturated ketone. For example carrying out the aldol condensation of acetone in the presence of hydrogen and of a hydrogenation catalyst will yield methyl isobutyl ketone (MIBK), as the final product.
The aldol condensation is a useful reaction for the production of higher ketones from lower, readily avalable ketones, and is extensively used for this purpose in the organic chemical industry. Acetone derivatives alone, most of which are prepared by some variant of an aldol condensation, make up a market of about 500 million pounds annually. Methyl isobutyl ketone (MIBK) alone makes up a major portion of the acetone derivatives market with about 200 million pounds produced annually. However, one difficulty frequently experienced in the use of the aldol condensation is its tendency to produce complex mixtures of products. The only structural requirements on the two condensing ketone molecules, apart from the presence of their oxo groups, is that the first ketone molecule possess at least one hydrogen atom on the carbon atom alpha to the oxo group. Since the product of the condensation is itself a ketone and normally has at least one hydrogen atom on the carbon atom alpha to the oxo group, the condensation product can undergo further condensation to produce additional products. Thus, depending on the catalyst and reaction conditions employed, the initial products of the condensation can react with more of the starting materials or with themselves to form oligomeric species or they can cyclize to form cyclic aliphatic or aromatic products. For example the MIBK initially produced by self-condensation of acetone in the presence of hydrogen can undergo further condensation with acetone to give diisobutyl ketone (DIBK).
In most aldol condensations it is, for economic reasons, desirable to optimize the production of only one of the numerous possible products. In a few cases, it may be desired to isolate more than one product (for example, the aldol condensation of acetone is used industrially to produce both MIBK and DIBK, both of which are of commercial value and these two ketones are easily separable by fractional distillation), but even in these cases it is desirable to be able to control the relative amounts of the products in order to match these relative amounts to market demands. Thus, catalysts which selectively catalyze the formation of selected ones of the numerous possible products greatly improve the commercial use of the aldol condensation.
Because molecular sieves can affect product distribution by shape selectivity, that is they can curtail the formation of products that do not have the proper shape to enter into or exit from the molecular sieve pores, they offer the opportunity to tailor the product distribution from an aldol condensation to maximize production of the desired products by appropriate choices of the molecular sieve catalyst and/or reaction conditions. Accordingly, several attempts have been made to use molecular sieves as catalysts in aldol condensations.
U.S. Pat. No. 4,339,606 issued July 13, 1982 to Huang et al. and assigned to Mobil Oil Corporation describes the use of palladium loaded ZSM-5 zeolite as a catalyst for the self-condensation of acetone under hydrogen at 600 psi. and 180.degree. C. to give MIBK. This patent claims a 98% selectivity to MIBK and no DIBK production but we have been unable to eliminate DIBK production using catalysts of similar pore size, composition or structure.
Golodets, G. I.; Pavlenko, N. V.; Korzhova, L. F.; Vaisberg, K. M.; Churkin, Yu. I., Kinet. Katal., 1984, 25, 1015 report the self-condensation of acetone metal-containing zeolites to give a mixture of products. Sumitomo Chemical Co. Ltd., German Offenlegungsschrift 1936203, published 20 July 1968, and British Pat. No. 1,252,335 published 3 November, Showa Denko K.K., Japanese Patent Application No. 72/13017 filed 20 Apr. 1972, Application No. 73/27288 filed 21 Aug. 1973, Application No. 73/27287 filed 21 Aug. 1973, and Application No. 73/26736 filed 15 Aug. 1973 report similar reactions.
U.S. Pat. No. 3,728,408 issued 17 Apr. 1973 to Tobias, U.S. Pat. No. 4,011,278 issued 8 May 1977 to Plank, Rosinski and Kerr, and U.S. Pat. No. 4,306,106 issued 15 Dec. 1981 to Kerr, Plank and Rosinski, all assigned to Mobil Oil Corporation, disclose by way of example the aldol condensation of acetone over aluminosilicate zeolites to give mesityl oxide and mesitylene but the catalyst contains no hydrogenation site. These reactions are also discussed in Chang, C. D.; Lang, W. H.; Smith, R. L., J. Catal, 1979, 56, 169 and Chang, C. D.; Silvestri, A. J., J. Catal, 1977, 47, 249, and are reviewed in Chang, C. D.; Lang, W. H.; Bell, W. K. in "Catalysis of Organic Reactions", Moser, W. R. (Ed.), Marcel Dekker: New York, 1981, pp 73-94.
The following papers:
Kuznetsov, O. I.; Shauki, M. Kh.; Panchekov, G. M., Khim, Kinet, Katal, 1979, 182; PA1 Guseinov, A. D.; Chasova, T. A.; Kuznetsov, A. I.; Panchenkov, G. M., Neft. Gaz. (Vinogradov, V. N. Ed.), 1974, 146; PA1 Kuznetsov. O. I.; Panchenkov, G. M.; Chasova, T. A.; Guseinov, A. D., Neftepererab. NeftKhim. (Moscow), 1973, 44; PA1 Kuznetsov, A. I.; Panchenkov, G. M.; Guseinov, A. M.; Chasova, T. A., Neftpererab. NeftKhim. (Moscow), 1973, 28; PA1 Isakov, Ya. I.; Minachev, Kh. M.; Usachev, N. Ya., Izv. Akad. Nauk. SSSR, Ser. Khim., 1972, 1175; PA1 Grigor'ev, A. A.; Guseva, S. I.; Pinkhasik, E. V.; Avrekh, G. L.; Sedlyarov, V. A.; Lunin, A. f., Khim. Prom-st. (Moscow), 1981, 73; and PA1 Guseva, S. I.; Grigor'ev, A. A.; Pinkhasik, E. V.; Avrekh, G. L., Neftpererab. NefteKhim. (Moscow), 1979, 45,
examine the condensation of acetone over traditional zeolites such as A, X, or Y zeolites but these materials show rather poor activity, selectivity and lifetime.
U.S. Pat. No. 4,433,174 issued 21 Feb. 1984 and U.S. Pat. No. 4,447,641 issued 8 May 1984, both to Hagen and both assigned to Standard Oil Company (Indiana) discuss the condensation of aldehydes or esters with formaldehyde to give alpha, beta unsaturated aldehydes or esters, respectively, using borosilicate molecular sieves as catalysts. Again, no hydrogenation takes place in these processes. U.S. Pat. No. 4,374,274 issued 15 Feb. 1983 to Hellen, Halbritter and Gramlich, and assigned to BASF describes the use of a palladium on metal phosphate catalyst to effect the condensation of ketones with formaldehyde under hydrogen to give methyl substituted ketones, but this catalyst is not a molecular sieve based catalyst.
Dworezkov et al., "Absorptive properties of aluminumphosphate molecular sieves", in Che and Bond (eds.), Adsorption and catalysis on oxide surfaces (Studies in Surface Science and Catalysis 21), pp. 163-172, (Elsevier, Amsterdam, 1985), discloses the adsorption of acetone on to the aluminophosphate AlPO.sub.4 -5 and subsequent desorption of mesityl oxide and other materials from the aluminophosphate.
It is also known that the closely related Knoevenagel condensation occurs over molecular sieves; see Taylor, G. A., J. Chem. Soc., Perkin Trans. I., 1981, 3132.
None of the molecular sieve catalysts described above are ideal for use in aldol condensations. In particular, some of the prior art molecular sieve catalysts frequently fail to achieve high selectivities to the desired products of aldol condensations when operated at the conversion rates required in industrial operation.
It has now been discovered that the use of certain non-zeolitic molecular sieves as catalysts in aldol condensations offers high selectivities and these high selectivities can be maintained at high conversions.